Antimicrobial peptides such as 2-defensins and cathelicidins provide the gingival epithelium with a first line of defense against pathogenic bacteria. In vitro and in vivo experiments have indicated a role for these peptides in the innate host defense as both direct antimicrobial agents and as chemokines which can link the innate and adaptive immune responses. Production of both classes of peptides is increased in gingival epithelial cells (GEC) by live bacteria and by bacterial products, suggesting the potential for modulating levels of these antibiotic agents therapeutically. More recently, expression of 2-defensins and the cathelicidin LL-37 were induced in myeloid cells and several cell lines by a less toxic agent, the hormonally active form of vitamin D, 1,25(OH)2-vitamin D3. This induction corresponded with an increase in antibacterial activity secreted by these cells as well. Our preliminary results demonstrate that 1,25(OH)2D3 can increase LL-37 mRNA levels in both airway epithelial cells (AEC) and GEC, and LL-37-dependent antibacterial activity in airway surface fluid of AEC grown in an air-liquid interface (ALI). Published data has demonstrated an association between polymorphisms of the vitamin D receptor (VDR) gene and early-onset periodontitis. Based upon these results, we hypothesize that physiological doses of Vitamin D can increase antimicrobial peptide expression and antibacterial activity of oral epithelial cells. The goal of this pilot study is to investigate the potential of vitamin D as an agent to aid in the innate immune defenses against oral pathogens. In this proposal we will focus on the induction of cathelicidin gene expression and activity against Aggregatibacter actinomycetemcomitans (Aa) in cell lines and in primary cultures of human gingival epithelium. To address our hypothesis, we propose to: 1) Quantify the vitamin D-mediated induction of antimicrobial peptide expression and antibacterial activity in primary cultures of gingival epithelial cells from healthy individuals, and compare the response with cells from periodontitis patients;and 2) Define the mechanism of induction of LL-37 in gingival cells by vitamin D by the examination of Vitamin D receptor element (VDRE)-mediated signal transduction pathways. Identification of a non- toxic agent that could increase antibacterial capabilities of the gingiva through transcriptional mechanisms could have long-reaching implications in the study of periodontal disease and oral infectious diseases in general. It is our hope that the results from this pilot study will be a foundation to develop an in-depth study of the utility of 1,25 (OH)2D3 to augment current therapies for periodontal disease. PUBLIC HEALTH RELEVANCE: Periodontal disease is caused by bacteria that adhere to and colonize the gingival cells adjacent to the teeth. To increase the ability of this tissue to prevent bacterial growth, investigators have examined the expression of small proteins with potent antibiotic activity, called antimicrobial peptides. We have shown that one of these peptides, LL- 37, can be increased in gingival cells by treatment with low doses of vitamin D. This proposal seeks to examine whether we can develop more in-depth studies of the potential for using vitamin D as a preventative treatment for periodontal disease.